The original version of this Article contained an error in Fig. 2b. The y-axis label in Fig. 2b was incorrectly labelled 'Snap-in force (μN)'. In the correct version, the axis is labelled 'Snap-in force (nN)'. In the original version of this Article, the "Butterfly wings" section of the Methods incorrectly stated the name of the butterfly as 'Golden bird'. In the correct version, the name of the butterfly is 'Golden birdwing'. These have now been corrected in both the PDF and HTML versions of the article.